Column Agglutination Test (“CAT” or “gel card” or “reagent card”) is one of the most common formats used in the field of immunohematology. Gel card is composed of a plurality of microtubes. This system for typing and screening blood is based on the sieving effect of a separation matrix. The test is typically performed in a microcolumn in which the red cell agglutinates are trapped in the separation matrix during centrifugation (in case of reaction between antigens and antibodies), and unagglutinated cells form a pellet at the bottom of the column (in the absence of reaction).
Cards are easy-to-use, easy-to-read and provide reliable results when used both manually and with automatic analyzers. However, storage of cards (generally at room temperature) induces a normal evaporation of supernatant. This shortens the shelf life of cards. The evaporated material condenses on the underside of the cover of the cards. Evaporation further leads to a lack of performance and stability. Additionally, abnormal transport conditions (the, mic stress, excessive shaking . . . ) could accelerate the degradation. In addition, for some tests such as Indirect Antiglobulin Test, samples and additional reagents (also referred to herein as the reactive medium) added into the reaction chamber of card are preferably physically separated from the gel (also referred to herein as the separation matrix) and the supernatant having anti-human globulin to achieve optimum performance and to avoid that a “neutralization phenomenon” occurs between the anti-human globulin and the sample, leading to weakened or falsely negative reactions. The gel and the supernatant mare referred hereinafter to as the reaction medium. One way to accomplish the physical separation between the reaction chamber and the reaction medium is by maintaining an airgap between the reaction medium and the reagents added to the reaction chamber. The absence of this air gap between gel and reactive medium may lead to decreased performance (Bobryk S. (2011). Variation in pipetting may lead to the decreased detection of antibodies in manual gel testing (Clinical Laboratory Science, 161-166) during Indirect Antiglobulin Test.